The invention relates to a process for the preparation of a 2-pyrrolidone by catalytic hydrogenation of succinonitrile, optionally carrying substituents, conducted in the liquid phase in the presence of ammonia followed by treating the hydrogenated product obtained with water.
In U.S. Pat. No. 4,123,438 a process is disclosed which can be operated with a good yield by suspending the hydrogenation catalyst in the liquid phase. The principle drawback to this method is that after the hydrogenation the catalyst must be separated, for instance by filtration. These separation processes are costly.
According to British Pat. No. 2,012,748, this drawback can be eliminated by using a fixed-bed catalyst. In such a process the succinonitrile to be hydrogenated is dissolved in liquid ammonia, passed over the fixed-bed hydrogenation catalyst. This eliminates the need for filtration or other methods to separate the catalyst from the reaction mixture.
It has now been found, however, that application of this fixed-bed catalyst process may reduce the catalyst activity to such an extent that it is necessary to renew the catalyst. Accordingly, it is an object of the present invention to provide an improved method for the hydrogenation of the succinonitrile in a fixed-bed reactor whereby catalyst renewal is eliminated, or is required less often.